With perhaps the unlikeliest final four in Bachelor Pad history, host Chris Harrison called tonight’s finale ”one of the wildest, craziest, most dramatic and devastatingly stunning shows you have ever seen.” Between unexpected romantic pairings (and triangles… and quadrangles), game-changing eliminations, and some truly ear-shattering karaoke, the path to tonight’s episode has been anything but smooth. Below, Harrison reveals why he found this season “scary” but now thinks it may be the best to date. Then, EW offers an exclusive clip showing an uncomfortable confrontation between two showmancers that sheds some light on why even a 10-year franchise vet like Harrison found Pad’s season-ender “hard to watch.”

ENTERTAINMENT WEEKLY: After last week’s karaoke challenge, have you officially retired “Sister Christian” from your iPod?CHRIS HARRISON: No way! First of all, I’m a kid of the ’80s, so I love it. [I was excited] when they told me we were doing that and we got to hang out for two or three hours with the guys as they were doing their sound check. We had a blast, it was so fun. The guys from Night Ranger were really cool about it. They kind of got the whole thing and put on a show for us. It was really neat.

You seemed surprised Nick performed as well as he did. I know you’ve been giving him some gentle ribbing in your blogs.It was a huge surprise. I didn’t know he was on the show! It was unbelievable. It is the craziest story that this guy has survived this long. I think he wasn’t interesting enough to vote out. There were bigger fish to fry each week because the alliances were trying to take each other – Erica versus Michael, and Chris and Blakeley. There were so many fights and so many battles that he was just kind of standing there, like, “All right.” He just survived. He didn’t make himself a big enough part of the game to be worthy of being voted out. Both alliances knew they could put him down whenever they wanted – they had the votes to get rid of him, so [they didn’t] worry about it. Nobody foresaw Erica changing the game so dynamically by taking Michael out. Then Rachel and Nick became a partnership. Then in that final challenge, the plan got away from [the dominant players]. You have to give him credit. He’s played it very well, and he’s survived. That’s what you have to do at Bachelor Pad – just survive.

This is a really unexpected final four. After she was voted out last week, Jaclyn said in anger that she would vote for Chris and Sarah.The Jaclyn-Rachel thing is very interesting. When you’re standing up there, and you know your best friend is going to take you with her – you’ve had this alliance and taken care of each other and done everything you’ve promised… [it seems like] of course Rachel’s going to choose Jaclyn. Honestly, Rachel would have. She tried, but Nick got the better of her that night and kind of took advantage of her. She regrets it, and she was sad, but she definitely stabbed Jaclyn in the back. Jaclyn was bitter about it, pissed – and she’s still mad about it. It’s something else that changes the game. Rachel, as sad as she was and upset and regretful, as a friend you would still think, “What the heck? How could you not have taken me with you in the end?” That’ll definitely come into play when they have to vote.

Going into the finale, what are the strengths and weaknesses for the final four?Well the weakness, obviously, for Chris and Sarah is that they’re not the most likable couple, but… you have to remember there are fans on that jury. The fans don’t really have an alliance. Then [Chris can count on] the other people that were in his alliance, so they have some votes already going in. Then there are a lot of swing votes this season. That was the main difference that you’ll see, and that’s what made Bachelor Pad different this season. You can usually look and you know all these people. Well, you don’t know all of them now, so there were a lot of swing votes up for grabs. As for, Chris and Sarah, say what you will about him, but he played the game well, and so did Sarah. They won challenges, and he schemed well, and he brought Erica into the voting booth and changed the game. You have to give him some credit in the way he played the game.

Then you look at Rachel and Nick, and they didn’t play the game. They [practically] just met a week ago and got thrown together. You could say Nick was a genius, but he was definitely a quiet genius. What did he do to really earn his [place in the finals]? Rachel really was riding on Michael’s coattails – she wasn’t calling the shots. As far as game playing goes, Chris and Sarah were far more dominant. That says a lot.

They all have their strengths and weaknesses. Obviously Rachel and Nick are a little more likable than Chris and Sarah, so is it a popularity contest? Is it gamesmanship? This definitely made for an interesting vote.

NEXT: Watch Michael get defensive during his reunion with Rachel, then learn why Harrison called the finale “disturbing”